Kidney production method

ABSTRACT

The present invention provides a kidney production method including a step of tissue-specifically removing a metanephric mesenchyme of a metanephros of a non-human animal; a step of transplanting, into the metanephros, a kidney precursor cell derived from a non-human animal which is allogeneic or xenogeneic to the non-human animal; and a step of advancing development of the metanephros, which is a step in which the transplanted kidney precursor cell is differentiated and matured to form a part of the kidney.

TECHNICAL FIELD

The present invention relates to a kidney production method. More specifically, the present invention relates to a kidney production method, a kidney, a non-human animal, an organ for transplantation, a kit for kidney production, a medical drug for kidney regeneration, a kidney transplantation method, and a method for treating a kidney disease. Priority is claimed on Japanese Patent Application No. 2016-129393, filed on Jun. 29, 2016, the content of which is incorporated herein by reference.

BACKGROUND ART

Due to aging and expansion of an adaptation disease, dialysis patients are increasing rapidly. The lives of these patients can be saved by dialysis medical treatment, but because dialysis does not compensate for all kidney functions, cardiovascular diseases of the patients tend to increase, thereby causing rise in mortality rates. In addition, the dialysis patients are overburdened with time and mental loads, which makes it difficult to return to society in many cases.

Furthermore, there are about 2 million patients with the end-stage renal disease requiring a kidney transplantation, and the number of patients tends to further increase due to the organ donor shortage. Therefore, the end-stage renal disease is a serious medical problem.

At present, various tissue-specific precursor cells or tissue stem cells can be induced from pluripotent stem cells such as iPS cells and ES cells (refer to, for example, Non-Patent Document 1). However, for example, the kidney is an organ with low self-repairing ability, and therefore the kidney function depends on a complicated structure composed of various kinds of cells. For this reason, current techniques have not yet reached a stage where kidneys having complicated three-dimensional structures can be regenerated from kidney precursor cells.

CITATION LIST Non-Patent Literature

-   [Non-Patent Document 1] Takasato M, et al., Directing human     embryonic stem cell differentiation towards a renal lineage     generates a self-organizing kidney, Nat. Cell Biol., 16 (1),     118-126, 2014.

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide a technique for producing a kidney from kidney precursor cells.

Solution to Problem

The present invention includes the following aspects.

(1) A kidney production method including a step of tissue-specifically removing a metanephric mesenchyme of a metanephros of a non-human animal; a step of transplanting, into the metanephros, a kidney precursor cell derived from a non-human animal which is allogeneic or xenogeneic to the non-human animal; and a step of advancing development of the metanephros, in which the transplanted kidney precursor cell is differentiated and matured to form a part of the kidney.

(2) The kidney production method according to (1), further including a step of tissue-specifically removing an ureteric bud of the metanephros; and a step of transplanting, into the metanephros, a kidney precursor cell derived from a non-human animal which is allogeneic or xenogeneic to the non-human animal.

(3) The kidney production method according to (1) or (2), in which the kidney precursor cell is a cat cell.

(4) The kidney production method according to any one of (1) to (3), in which the non-human animal is a pig.

(5) The kidney production method according to any one of (1) to (3), in which the non-human animal is a mouse.

(6) The kidney production method according to any one of (1) to (3), in which the non-human animal is a cat.

(7) A kidney produced by the production method according to any one of (1) to (6).

(8) A kidney including: a cell derived from a non-human animal; and a cell derived from a non-human animal which is allogeneic or xenogeneic to the non-human animal, in which a proportion of the cell derived from the non-human animal which is allogeneic or xenogeneic to the non-human animal is 70% by mass or more.

(9) The kidney according to (8), in which the cell derived from the non-human animal which is allogeneic or xenogeneic to the non-human animal is a cat cell.

(10) A non-human animal comprising the kidney according to any one of (7) to (9).

(11) An organ for transplantation including: the kidney according to any one of (7) to (9); a ureter; and a bladder.

(12) The organ for transplantation according to (11), in which the ureter and the bladder are derived from a non-human animal.

(13) A kit for kidney production including: a metanephros of a non-human animal; a medicine which tissue-specifically removes a metanephric mesenchyme of the metanephros; and a kidney precursor cell derived from a non-human animal which is allogeneic or xenogeneic to the non-human animal.

(14) The kit for kidney production according to (13), further including a medicine which tissue-specifically removes an ureteric bud of the metanephros.

(15) A medical drug for kidney regeneration including: a metanephros of a non-human animal; a medicine which tissue-specifically removes a metanephric mesenchyme of the metanephros; and a kidney precursor cell derived from a non-human animal.

(16) The medical drug for kidney regeneration according to (15), further including a medicine which tissue-specifically removes an ureteric bud of the metanephros.

(17) A kidney transplantation method including: a step of transplanting the organ for transplantation according to claim 11 or 12 into a body of an affected animal; and a step of connecting a bladder of the organ for transplantation to a ureter of the affected animal at a predetermined time after the transplantation.

(18) A method for treating a kidney disease, including: a step of transplanting a metanephros and a cloaca of a non-human animal into a body of an affected animal;

a step of tissue-specifically removing a metanephric mesenchyme of a metanephros; a step of transplanting a kidney precursor cell into the metanephros, in which the transplanted kidney precursor cell is differentiated and matured to form a part of a kidney, and the cloaca is differentiated and matured to form a bladder so as to connect the bladder to the kidney via a ureter; and a step (b) of connecting the bladder to a ureter of the affected animal at a predetermined time after the transplantation of the kidney precursor cell.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a technique for producing a kidney from kidney precursor cells.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a fetus of a mouse at around day 11 of embryonic development.

(a) to (c) of FIG. 2 are schematic diagrams for explaining how a kidney is developed.

FIG. 3 is a photograph showing a result of immunostaining of a kidney tissue sample in Experimental Example 3.

FIG. 4 is a photograph showing a result of immunostaining of a kidney tissue sample in Experimental Example 4.

(a) and (b) of FIG. 5 are photographs of a kidney regenerated in a mouse body in Experimental Example 5.

(a) and (b) of FIG. 6 are microphotographs of tissue section samples of the kidney regenerated in the mouse body in Experimental Example 5.

(a) to (c) of FIG. 7 are photographs showing results of immunostaining of a tissue sample of a metanephros in Experimental Example 6.

DESCRIPTION OF EMBODIMENTS

[Kidney Production Method]

FIG. 1 is a schematic diagram showing a fetus of a mouse at around day 11 of embryonic development. A kidney is formed through three stages of pronephros, mesonephros, and metanephros. Among these, the pronephros and mesonephros are degenerated later. A kidney functioning in an adult body of mammals is the metanephros.

As shown in FIG. 1, the kidney is formed by an interaction between an ureteric bud and a metanephric mesenchyme surrounding the ureteric bud. The ureteric bud constitutes from collecting ducts to a ureter, and nephron precursor cells contained in the metanephric mesenchyme are the origin of glomeruli and kidney tubules. In the present specification, a kidney development region including the ureteric bud and the metanephric mesenchyme is called a kidney development niche.

In one embodiment, the present invention provides a kidney production method including a step (i) of tissue-specifically removing a metanephric mesenchyme of a metanephros of a non-human animal; a step (ii) of transplanting, into the metanephros, a kidney precursor cell derived from a non-human animal which is allogeneic or xenogeneic to the non-human animal; and a step (iii) of advancing development of the metanephros, which is a step in which the transplanted kidney precursor cell is differentiated and matured to form a part of the kidney.

In the related art, efficiency of a cell transplant into a kidney development niche was extremely poor in terms of fixation. On the other hand, as described later in Examples, according to a production method of the present embodiment, transplanted kidney precursor cells can be engrafted with high efficiency. In addition, the transplanted kidney precursor cells take over a development program of a host and autonomously advance complicated differentiation induction to form a part of the kidney.

A kidney production method of the present embodiment will be described in more detail with reference to FIG. 2. (a) to (c) of FIG. 2 are schematic diagrams for explaining how a kidney is developed. Among these, (a) of FIG. 2 corresponds to the kidney production method of the present embodiment.

In (a) of FIG. 2, a metanephric mesenchyme of an early kidney of a non-human animal embryo is removed by adding a removing medicine. The addition results in a state in which kidney stem cells derived from the host do not exist, that is, a state in which the niche is empty. Subsequently, new kidney precursor cells (kidney stem cells) are transplanted into this kidney development niche. Then, the transplanted kidney precursor cells are fixed and take over the development program of the host to proceed the development of the kidney. As a result, the kidney is regenerated by the transplanted kidney precursor cells.

Meanwhile, in (b) of FIG. 2, a metanephric mesenchyme of an early kidney of a non-human animal embryo is removed by adding a removing medicine. The addition results in a state in which kidney stem cells derived from the host do not exist, that is, a state in which the niche is empty. In (b) of FIG. 2, a transplantation of new kidney precursor cells is not carried out. Even if the development of the kidney progresses in this state, the kidney will be degenerated.

In addition, in (c) of FIG. 2, new kidney precursor cells are transplanted into the metanephric mesenchyme of the early kidney of the non-human animal embryo while remaining the kidney stem cells derived from the host. However, competition by the existing cells derived from the host which occupies the kidney development niche is strong, and thus the transplanted kidney precursor cells are not fixed. As a result, a kidney composed of the cells derived from the host is formed.

Hereinafter, each step of the kidney production method of the present embodiment will be described in detail.

(Step (i))

In the present step, the metanephric mesenchyme of the non-human animal embryo is tissue-specifically removed. The non-human animal is not particularly limited, and may be, for example, a pig. Pigs are suitable for a transplantation into a human because of a size of organs thereof, and genetic modification techniques have also been established. Alternatively, the non-human animal may be a mouse. Mice are easy to use because genetic modification techniques and various experimental systems have been established. Alternatively, the non-human animal may be a cat. Cats are one of the most common animals as a pet, but are an animal having a very high incidence of chronic kidney disease. For example, there are reports that about 30% of the cause of cat death is chronic kidney failure and 50% or more of cats die or are euthanized due to a deterioration in kidney functions. For this reason, there is a potential demand for the kidney transplantation as one of life-prolonging techniques for cats suffering from kidney disease.

Tissue-specific removal of the metanephric mesenchyme is not particularly limited as long as the metanephric mesenchyme can be tissue-specifically removed, and can be performed by using, for example, a genetic recombination technique.

A more specific method of tissue-specifically removing the metanephric mesenchyme will be described by using a mouse system as an example. Examples of the method of tissue-specific removal of the metanephric mesenchyme include a method in which an iDTR mouse expressing a diphtheria toxin receptor (DTR) in a Cre recombinase activity-dependent manner is crossed with Six2-Cre mouse in which a Cre recombinase gene is introduced into downstream of a promoter of Six2; and the diphtheria toxin is brought into contact with the metanephros tissue of a progeny to be obtained.

The iDTR mouse has a transcription termination sequence flanked by two loxP sequences upstream of a gene encoding the diphtheria toxin receptor. For this reason, the diphtheria toxin receptor is not expressed in this state. However, if the transcription termination sequence flanked by the two loxP sequences is removed by the Cre recombinase, the diphtheria toxin receptor is expressed.

Since mice do not have the diphtheria toxin receptor, cells of mice are not killed even if the diphtheria toxin is brought into contact with the cells thereof. However, it is known that when the diphtheria toxin is brought into contact with cells of a mouse expressing the diphtheria toxin receptor, the cells are killed. In the above-described example, this phenomenon is utilized.

First, if the iDTR mouse is crossed with the Six2-Cre mouse specifically expressing the Cre recombinase in the metanephric mesenchyme, a mouse tissue-specifically expressing the diphtheria toxin receptor in the metanephros tissue among progenies to be obtained. Six2 is a transcription factor that is specifically expressed in the metanephric mesenchyme.

Subsequently, when the diphtheria toxin is brought into contact with the metanephros of the above-mentioned mouse, cells specifically in the metanephric mesenchyme are killed, and thus the metanephric mesenchyme can be tissue-specifically removed. That is, the kidney development niche can be emptied.

The contact with the diphtheria toxin may be carried out by injecting the diphtheria toxin into a parent mouse or a fetus of a mouse. Alternatively, the contact may be carried out by extracting the metanephros from a fetus of a mouse, organ-culturing the extracted metanephros, adding the diphtheria toxin to a medium, and the like. Alternatively, the contact may be carried out by transplanting the extracted metanephros into a para-aortic region or greater omentum of an affected animal, locally administering the diphtheria toxin into a body of the affected animal, and the like. In the present specification, examples of the affected animal include cats, dogs, horses (especially race horses), monkeys, cows, sheep, pigs, goats, rabbits, hamsters, guinea pigs, rats, mice, and the like.

The above-described method is one of methods of tissue-specifically removing the metanephric mesenchyme, and can be applied to not only mice but also any non-human animal.

(Step (ii))

Subsequently, in the present step, kidney precursor cells derived from a non-human animal which is allogeneic or xenogeneic to the non-human animal are transplanted into the metanephros. The step (i) and step (ii) may be carried out in parallel. That is, a time of emptying the niche and a time of transplanting the kidney precursor cells may overlap. For example, the addition of the removing medicine and the transplantation of the kidney precursor cells may be carried out at the same time.

Examples of the kidney precursor cells include kidney precursor cells (kidney stem cells) differentiation-induced from pluripotent stem cells such as mesenchymal stem cells (MSCs), iPS cells, and ES cells derived from mammals. The kidney precursor cells may be cells derived from an affected animal or allogeneic cells whose rejection reaction is suppressed in an affected animal.

It is preferable that the kidney precursor cells be cells derived from an affected animal that is a subject of the transplantation of the kidney after production. Examples of the kidney precursor cells differentiation-induced from mesenchymal stem cells sorted from bone marrow, adipose tissue, bloodshed, or umbilical cord blood, which is derived from an affected animal. The kidney precursor cells may be kidney precursor cells differentiation-induced from mesenchymal stem cells sorted from bone marrow, bloodshed, or umbilical cord blood of an affected animal itself. A sorting method may be a method according to general surgical medical techniques. It is preferable that the sorted cells be cultivated for 2 to 5 times by selecting optimum conditions. In addition, the cultivation may be carried out by using a medium kit exclusive for human mesenchymal stem cells manufactured by Cambrex BioScience, or the like for the purpose of continuing the cultivation while suppressing the transformation of the mesenchymal stem cells.

If desired, a desired gene may be introduced into the kidney precursor cells using adenovirus, retrovirus, or the like. For example, the gene may be introduced so as to express glial cell line-derived neurotrophic factor-GDNF for the purpose of assisting kidney formation. This is because the mesenchymal tissue immediately before the kidney is formed becomes to express GDNF, and the ureteric bud expressing c-ret which is a receptor thereof is drawn, thereby completing a first important step of the kidney development.

As a method of the transplantation, for example, the kidney precursor cells derived from the non-human animal may be injected into the metanephros using an injection needle or the like. The number of kidney precursor cells to be transplanted is preferably about 1×10³ to 1×10⁶, for example. Because the transplantation of the kidney precursor cells can be performed in vitro, skill for the operation is not required, and the operation is easily performed.

The kidney precursor cells may be cat cells. In this case, the kidney to be produced is composed of cat cells transplanted into the kidney development niche. This kidney can be transplanted into a cat that is an affected animal so as to function. The kidney precursor cells are more preferably cells in which the rejection reaction with cells of the affected animal or the affected animal is suppressed.

The kidney precursor cells may be cells derived from the non-human animal other than cats. Examples of non-human animal other than cats include the above-mentioned affected animal. In this case, the kidney to be produced is composed of cells derived from the non-human animal which are transplanted into the kidney development niche. This kidney can be transplanted into the non-human animal that is the affected animal so as to function. The kidney precursor cells are more preferably cells in which the rejection reaction with cells of the affected animal or the affected animal is suppressed.

(Step (iii))

Subsequently, in the present step, the development of the metanephros after transplanting the kidney precursor cells progresses. As a result, the transplanted kidney precursor cells are differentiated and matured, thereby forming a part of the kidney. In a case where the kidney precursor cells are transplanted without extracting the metanephros from the embryo, the progression of the metanephros can be carried out by returning the embryo back to the uterus of the parent animal, performing whole embryo culture, and the like. Alternatively, in a case where the metanephros is extracted to transplant the kidney precursor cells, the progression can be carried out by continuing an organ culture of the metanephros. Alternatively, in a case where the metanephros is transplanted into the para-aortic region or greater omentum of the affected animal to transplant the kidney precursor cells into the body of the affected animal, the progression can be carried out by growing the metanephros as it is.

As a result, as will be described later in Examples, the transplanted kidney precursor cells take over the developmental program of the host, autonomously advance complicated differentiation induction while interacting with the remaining ureteric bud, and thereby forming the glomeruli and kidney tubules. In addition, in order to completely remove the kidney precursor cells constituting the metanephric mesenchyme on the host side, the glomeruli and kidney tubules to be regenerated are composed only of cells derived from substantially the transplanted kidney precursor cells.

The term “substantially” means that in a case where the kidney is produced using the kidney development niche of the non-human animal, mixing of cells other than the transplanted kidney precursor cells is not excluded. In other words, it is preferable that 70% by mass or more of the glomeruli and kidney tubules to be regenerated be composed of the transplanted kidney precursor cells, it is more preferable that 80% by mass or more of the glomerulus and kidney tubules to be regenerated be composed of the transplanted kidney precursor cells, it is even more preferable that 90% by mass or more of the glomerulus and kidney tubules to be regenerated be composed of the transplanted kidney precursor cells, it is still more preferable that 95% by mass or more of the glomerulus and kidney tubules to be regenerated be composed of the transplanted kidney precursor cells, and it is particularly preferable that 99% by mass or more of the glomerulus and kidney tubules to be regenerated be composed of the transplanted kidney precursor cells.

The kidney production method of the present embodiment may further include a step (iv) of tissue-specifically removing an ureteric bud of the metanephros; and a step (v) of transplanting, into the metanephros, a kidney precursor cell derived from a non-human animal which is allogeneic or xenogeneic to the non-human animal. In addition, the steps (iv) and (v) may be performed before the steps (i) to (iii) described above, or may be performed after the steps (i) to (iii) described above. Furthermore, the step (iii) may further be carried out after the steps (iv) and (v).

As a result, not only the metanephric mesenchyme but also the ureteric bud can be replaced with cells derived from the transplanted kidney precursor cells. As a result, it is possible to produce the kidney substantially consisting only of the cells derived from the transplanted kidney precursor cells derived from the non-human animal. Hereinafter, each step will be described.

(Step (iv))

In the present step, the ureteric bud of the metanephros of the non-human animal is tissue-specifically removed. The tissue-specific removal of the ureteric bud is not particularly limited as long as the ureteric bud can be tissue-specifically removed, and can be performed by using, for example, a genetic recombination technique.

For example, it is possible to use a mouse obtained by further introducing a gene encoding a Cre-ER protein into downstream of an ureteric bud-specific promoter in the mouse obtained by crossing the iDTR mouse and the Six2-Cre mouse described above. Examples of the ureteric bud-specific promoter include a promoter of cytokeratin 8, a promoter of HoxB7, and the like.

Examples of such a mouse include an iDTR mouse having a genotype of Six2-Cre^(tg/wt) cytokeratin 8-Cre-ER^(tg/wt), an iDTR mouse having a genotype of Six2-Cre^(tg/wt)HoxB7-Cre-ER^(tg/wt), and the like. The term “tg” represents that the type is transgenic, and “wt” represents a wild type.

The Cre-ER protein is a fusion protein of a Cre recombinase and a mutant estrogen receptor. The above-described mouse expresses Cre-ER in a promoter-dependent manner with respect to cytokeratin 8 or HoxB7, which is a marker for the ureteric bud.

Although the Cre-ER protein is generally present in the cytoplasm, the Cre-ER protein is translocated into the nucleus by binding with tamoxifen, which is an estrogen derivative, and recombines against the loxP sequence. By utilizing the above description, It is possible to tamoxifen-dependently adjust a working time of a Cre-loxP system. Therefore, even if Cre-ER and Cre are expressed at the same time, it is possible to control the expression of Cre-ER activity depending on whether tamoxifen is administered or not. Cre-ERT, Cre-ERT2, or the like, which is a modified form of Cre-ER, may be used instead of Cre-ER.

The mouse described above expresses the diphtheria toxin receptor specifically in the metanephric mesenchyme. In this case, it is preferable to first perform the steps (i), (ii), and (iii) described above. Specifically, the metanephric mesenchyme is removed by bringing the diphtheria toxin into contact with the metanephros of the mouse embryo. Subsequently, the kidney precursor cells derived from the non-human animal are transplanted into the metanephros by the above-described method so that the development of the metanephros progresses. As a result, the metanephric mesenchyme is regenerated by the transplanted kidney precursor cells derived from the non-human animal.

Subsequently, when tamoxifen is brought into contact with this metanephros, the diphtheria toxin receptor is expressed specifically in the ureteric bud. In this case, by bringing the diphtheria toxin into contact with this metanephros, the ureteric bud can be tissue-specifically removed. That is, the kidney development niche can be emptied.

In the above example of the mouse, the gene encoding the Cre protein is introduced into downstream of the metanephric mesenchyme-specific promoter, and the gene encoding the Cre-ER protein is introduced into downstream of the ureteric bud-specific promoter. However, the gene encoding the Cre-ER protein may be introduced into downstream of the metanephric mesenchyme-specific promoter, and the gene encoding the Cre protein may be introduced into downstream of the ureteric bud-specific promoter. In addition, Cre-ERT, Cre-ERT2, or the like, which is a modified form of Cre-ER, may be used instead of Cre-ER.

For example, a mouse obtained by further introducing the gene encoding the Cre protein into downstream of the ureteric bud-specific promoter in the mouse obtained by crossing the iDTR mouse with the mouse in which the gene encoding the Cre-ER protein is introduced into downstream of the metanephric mesenchyme-specific promoter, may be used.

More specific examples of the mouse include an iDTR mouse having a genotype of Six2-Cre-ER^(tg/wt)HoxB7-Cre^(tg/wt), and the like. The terms “tg” and “wt” have the same meanings as those described above.

This mouse expresses Cre-ER specifically in the metanephric mesenchyme. In addition, the diphtheria toxin receptor is specifically expressed in the ureteric bud. Therefore, in the case of using this mouse, the steps (iv) and (v) are carried out before carrying out the steps (i) to (iii). Specifically, by bringing the diphtheria toxin into contact with the metanephros of the mouse embryo, the ureteric bud can be removed.

The above-described method is one of methods of tissue-specifically removing the ureteric bud, and can be applied to not only mice but also any non-human animal.

(Step (v))

Subsequently, in the present step, the kidney precursor cells derived from the non-human animal which is allogeneic or xenogeneic to the non-human animal are transplanted into the metanephros so that the development of the ureteric bud progresses. As a result, the ureteric bud is regenerated by the transplanted human kidney precursor cells. The step (iv) and step (v) may be carried out in parallel. That is, a time of emptying the niche and a time of transplanting the kidney precursor cells may overlap. For example, the addition of the removing medicine and the transplantation of the kidney precursor cells may be carried out at the same time.

Subsequently, the above-described step (iii) is carried out so that the development of embryos (metanephros) transplanted with the kidney precursor cells derived from the non-human animal progresses. As a result, the transplanted kidney precursor cells derived from the non-human animal are differentiated and matured, thereby forming a part of the kidney.

As the kidney precursor cells derived from the non-human animal, cells that are the same as those described above can be used. In a case where the kidney precursor cells have the same origin as the kidney precursor cells in the regeneration of the metanephric mesenchyme described above, not only the glomeruli and kidney tubules but also the collecting ducts and ureter are composed of cells of the same origin in the kidney to be produced.

Therefore, if the kidney precursor cells are cells derived from the affected animal or cells in which the rejection reaction with the affected animal is suppressed, it is possible to produce the kidney with less rejection reaction in a case of transplanting these kidney precursor cells into the affected animal.

For example, in a case where the steps (iv) and (v) are performed first using the iDTR mouse having the genotype of Six2-Cre-ER^(tg/wt)HoxB7-Cre^(tg/wt), the steps (i), (ii), and (iii) described above may be subsequently carried out. That is, when tamoxifen is brought into contact with the metanephros of the mouse whose ureteric bud has been regenerated by transplanted kidney precursor cells derived from the non-human animal, the diphtheria toxin receptor is expressed specifically in the metanephric mesenchyme in this case. Therefore, in this case, by bringing the diphtheria toxin into contact with this metanephros, the metanephric mesenchyme can be tissue-specifically removed in this case. That is, the kidney development niche can be emptied.

The above-described method is one of methods of tissue-specifically removing the ureteric bud, and can be applied to not only mice but also any non-human animal.

In the kidney production method of the present embodiment, any of the removal of the metanephric mesenchyme and the removal of the ureteric bud may be performed first. In a case of removing the ureteric bud first, the above-described Cre-loxP system may be appropriately modified.

In addition, in the kidney production method of the present embodiment, a system for killing cells can be used without particular limitation as long as the system can be applied to a target non-human animal species and can be operated in a tissue-specific manner or in a time-specific manner.

Therefore, a configuration in which the cells are killed by a system other than the diphtheria toxin receptor may be adopted. Examples thereof include a system that expresses a diphtheria toxin A subunit (DT-A) at downstream of a tissue-specific promoter in the Cre recombinase activity-dependent manner. This system can be applied to non-human animals which are originally sensitive to the diphtheria toxin. Examples of such a non-human animal include a pig.

Alternatively, examples thereof include a system that expresses a herpes simplex virus-derived thymidine kinase gene (HSV-TK) which induces apoptosis by administration of ganciclovir, at downstream of the tissue-specific promoter. In cells expressing HSV-TK, cell death is induced under administration of ganciclovir.

Alternatively, a system that induces apoptosis by dimerizing Caspase-3, Caspase-8, Caspase-9, and the like by administration of AP20187 may be used.

The kidney production method of the present embodiment is not limited to the method described above as long as the metanephric mesenchyme or the ureteric bud of the metanephros can be tissue-specifically removed, and it is possible to use various genetic recombination systems and a combination of genetic recombination systems.

[Kidney]

In one embodiment, the present invention provides a kidney produced by the production method described above. The kidney of the present embodiment is produced from the kidney precursor cells derived from a desired non-human animal by utilizing the kidney development niche and the developmental program of a host non-human animal. Therefore, the kidney can be transplanted into the affected animal so as to function.

As described above, the kidney of the present embodiment is formed by replacing the metanephric mesenchyme or the ureteric bud, or both thereof with the transplanted kidney precursor cells derived from the non-human animal. For this reason, in particular, in a case of the kidney in which both metanephric mesenchyme and ureteric bud are replaced with the transplanted kidney precursor cells derived from the non-human animal, this kidney is substantially composed only of cells derived from the transplanted kidney precursor cells derived from the non-human animal. For this reason, merely by specifying the cells constituting the kidney, it is difficult to specify whether a kidney is the kidney produced by the above-described production method, or is a kidney of an affected animal from which the transplanted kidney precursor cells derived from the non-human animal had been prepared.

The kidney includes cells derived from a non-human animal; and cells derived from a non-human animal which is allogeneic or xenogeneic to the non-human animal, in which a proportion of the cells derived from the non-human animal which is allogeneic or xenogeneic to the non-human animal is 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 99% by mass or more.

Examples of the non-human animals include pigs, mice, cats, and the like as described above. In addition, examples of the cells derived from a non-human animal which is allogeneic or xenogeneic to these non-human animals include the cells derived from the affected animal described above, and the like. Such a kidney can be produced by the above-described kidney production method.

The kidney of the present embodiment may be formed by replacing the kidney precursor cells derived from the non-human animal, which are transplanted with the metanephric mesenchyme by the above-described production method, for example. In this case, the collecting ducts and ureter derived from the ureteric bud are derived from a host non-human animal.

Alternatively, the kidney of the present embodiment may be formed by replacing the kidney precursor cells derived from the non-human animal, which are transplanted with the ureteric bud by the above-described production method. In this case, the glomeruli and kidney tubules derived from the metanephric mesenchyme are derived from a host non-human animal.

Alternatively, the kidney of the present embodiment may be formed by replacing the kidney precursor cells derived from the non-human animal, which are transplanted with both metanephric mesenchyme and ureteric bud by the above-described production method. In this case, the kidney is a kidney derived from the kidney precursor cells derived from the non-human animal, to which substantially all of the glomeruli, kidney tubules, collecting ducts, and ureter are transplanted. However, cells derived from a host non-human animal may remain in the formed kidney in some cases.

[Organ for Transplantation]

In one embodiment, the present invention provides an organ for transplantation including any of the kidney, ureter, and bladder described above.

The inventors of the present invention have previously been able to generate urine by transplantation of regenerated kidneys. However, the inventors have found that generated urine could not be excreted, which resulted in hydronephrosis, and therefore kidney functions could not be maintained for a long time. The inventors of the present invention also have found that, by transplanting a structure including not only the kidney but also the kidney, the ureter, and the bladder, not only generation of urine but also excretion of the generated urine is possible.

Therefore, since the organ for transplantation of the present embodiment includes the kidney, the ureter, and the bladder, even in a case where this organ is transplanted into an affected animal, not only generation of urine but also excretion of the generated urine is possible, and kidney functions can be maintained for a long time.

The organ for transplantation of the present embodiment may be transplanted into the para-aortic region or greater omentum of the affected animal, and may be transplanted into, for example, the spleen (around the splenic artery) of the affected animal. In addition, the bladder constituting the organ for transplantation described above may be connected to the ureter of the affected animal. In this manner, an organ structure in which the kidney, a first ureter, a first bladder, a second ureter, and a second bladder are connected in this order is formed. The second ureter and the second bladder are the ureter and bladder that the affected animal has inherently.

By forming such an organ structure, excretion of the urine generated by the regenerated kidneys constituting the above-described organ for transplantation becomes easier.

In the organ for transplantation of the present embodiment, the ureter (first ureter) and the bladder (first bladder) may be derived from the non-human animal in the kidney production method described above. Because the ureter and bladder generally have low immunogenicity, a problem is less likely to occur even if the ureter and the bladder are derived from an animal xenogeneic to the non-human animal. The non-human animal is a host animal which provides the kidney development niche serving as a scaffold in the kidney production method described above. That is, the organ for transplantation of the present embodiment may be composed of the kidney formed by the above-described production method, a ureter, and a bladder.

The organ for transplantation of the present embodiment can be extracted from a non-human animal, stored, and distributed while being in a state where the kidney, ureter, and bladder are connected to each other. The organ for transplantation may be frozen for storage and distribution. Alternatively, the organ for transplantation of the present embodiment can be distributed in a form of a non-human animal having the organ for transplantation of the present embodiment.

[Kit for Kidney Production]

In one embodiment, the present invention provides a kit for kidney production including a metanephros of a non-human animal; a medicine that tissue-specifically removes a metanephric mesenchyme of the embryo; and a kidney precursor cell derived from a non-human animal which is allogeneic or xenogeneic to the non-human animal.

By carrying out the above-mentioned kidney production method using the kit of the present embodiment, the kidney can be produced. Examples of the non-human animals include pigs, mice, cats, and the like as described above. The metanephros of the non-human animal may be provided in a form of an embryo or may be provided in a form of a parent animal including a fetus. In addition, the metanephros may be in a state of being connected to a cloaca which later becomes the bladder. In this case, the metanephros forms the kidney and ureter, the cloaca forms the bladder, and therefore a state in which these kidneys, ureters, and bladders are connected is formed. As a result, as described above, the produced kidneys are capable of not only generating urine but also excreting the produced urine.

In the kit of the present embodiment, examples of the medicine that tissue-specifically removes the metanephric mesenchyme include the above-mentioned diphtheria toxin, and the like. In this case, examples of a non-human animal include a non-human animal that expresses the diphtheria toxin receptor specifically in the metanephric mesenchyme by the Cre-loxP system or the like.

Alternatively, various conditional knockout systems other than those described above can also be used as long as the metanephric mesenchyme can be tissue-specifically removed thereby. As the medicine for tissue-specifically removing the metanephric mesenchyme, diphtheria toxin (iDTR system), tamoxifen (Cre-ERT2 system), tacrolimus (Mos-iCsp3 system), doxycycline, tetracycline (Tet-On/off system), ganciclovir (herpes virus-derived thymidine kinase gene system), and the like can be used depending on a system to be used.

These conditional knockout systems can be produced using genome editing techniques and the like, and can tissue-specifically remove cells in the kidney development niche of the non-human animal. In addition, a time at which cells are removed can be controlled by administering the medicine. By using these systems, it is possible to spatiotemporal-specifically control the removal of target cells and construct a living scaffold suitable for the kidney regeneration.

A method for administering the medicine that tissue-specifically removes the metanephric mesenchyme is not particularly limited, and may be appropriately selected according to the medicine to be used. Examples thereof include addition to a medium such as organ culture in vitro, local administration in vivo, intraperitoneal administration, intravenous injection, oral administration, and the like.

In addition, examples of the kidney precursor cells derived from a non-human animal which is allogeneic or xenogeneic to the non-human animal include the kidney precursor cells derived from the affected animal described above, and the like. Examples of the kidney precursor cells include kidney precursor cells differentiation-induced from iPS cells, mesenchymal stem cells (MSCs), and the like which are derived from an affected animal; kidney precursor cells differentiation-induced from allogeneic iPS cells or ES cells, in which the rejection reaction in an affected animal is suppressed; and the like. The allogeneic iPS cells described above can be obtained from, for example, a cell bank or the like.

The kidney production may be performed outside the body of the affected animal, and then the kidney may be transplanted into the para-aortic region or greater omentum of the affected animal. Alternatively, the kidney production may be performed in the body of the affected animal. More specifically, the kidney may be produced by transplanting the metanephros of the non-human animal into the para-aortic region or greater omentum of the affected animal first, emptying the niche of the metanephros in the body of the affected animal, and transplanting the kidney precursor cells. This method is advantageous in that a vascular system drawn into the regenerated kidney becomes a blood vessel of the affected animal, and that a functional kidney can be constructed.

The kit of the present embodiment may further include a medicine that tissue-specifically removes the ureteric bud of the metanephros. Accordingly, it is possible to produce a kidney derived from the kidney precursor cells transplanted with not only tissues derived from the metanephric mesenchyme but also tissues derived from the ureteric bud.

Examples of the medicine that tissue-specifically removes the ureteric bud include a combination of tamoxifen and diphtheria toxin as described above, and the like. In this case, examples of a non-human animal include a non-human animal that expresses the diphtheria toxin receptor specifically in the metanephric mesenchyme by the Cre-loxP system or the like, and also expresses the diphtheria toxin receptor specifically in the ureteric bud by administration of tamoxifen.

Alternatively, any of the various conditional knockout systems described above can be used to remove the ureteric bud. In this case, the medicine that tissue-specifically removes the ureteric bud becomes an appropriate medicine according to an adopted system.

By combining the above-described various conditional knockout systems, it is possible to remove a plurality of target tissues at any timing. For example, after tissue-specifically removing the ureteric bud by using tamoxifen, the metanephric mesenchyme can be tissue-specifically removed by using tacrolimus in a stepwise manner. As a result, almost all of the kidney tissues can be tissues derived from the transplanted kidney precursor cells.

[Medical Drug for Kidney Regeneration]

In one embodiment, the present invention provides a medical drug for kidney regeneration including a metanephros of a non-human animal; a medicine that tissue-specifically removes a metanephric mesenchyme of the metanephros; and a kidney precursor cell derived from a non-human animal.

According to the medical drug of the present embodiment, it is possible to perform the regeneration of the kidney within the body of the affected animal as described above. The medical drug of the present embodiment can be used as follows. First, the metanephros of a non-human animal is transplanted into the para-aortic region or greater omentum of the affected animal. Examples of the affected animal include those mentioned above. As the metanephros of the non-human animal, the same metanephros as in the above-described kit for kidney production can be used.

Subsequently, the medicine that tissue-specifically removes the metanephric mesenchyme is administered to the affected animal. As the medicine, the same medicine as in the above-described kit for kidney production can be used. It is preferable that the administration of the medicine be appropriately carried out by local administration, intraperitoneal administration, intravenous injection, oral administration, and the like depending on the medicine to be used.

Subsequently, the kidney precursor cells derived from the non-human animal are transplanted. Examples of the kidney precursor cells derived from the non-human animal include kidney precursor cells differentiation-induced from iPS cells, mesenchymal stem cells (MSCs), and the like which are derived from an affected animal; kidney precursor cells differentiation-induced from pluripotent stem cells such as allogeneic iPS cells or ES cells, in which the rejection reaction in an affected animal is suppressed; and the like. Thereafter, the development of the transplanted metanephros progresses, thereby producing (regenerating) the kidney composed of the kidney precursor cells transplanted into the body of the affected animal.

This medical drug of the present embodiment is advantageous in that a vascular system drawn into the regenerated kidney becomes a blood vessel of the affected animal, and that a functional kidney can be constructed.

The medical drug for kidney regeneration may further include a medicine that tissue-specifically removes that is configured to tissue-specifically remove the ureteric bud of the metanephros. Accordingly, it is possible to regenerate a kidney derived from the kidney precursor cells transplanted with not only tissues derived from the metanephric mesenchyme but also tissues derived from the ureteric bud. As the medicine that tissue-specifically removes the ureteric bud of the metanephros, the same medicine as in the above-described kit for kidney production can be used.

[Kidney Transplantation Method]

In one embodiment, the present invention provides a kidney transplantation method including: a step (a) of transplanting the organ for transplantation which has the kidney, ureter, and bladder described above into a body of an affected animal; and a step (b) of connecting a bladder of the organ for transplantation to a ureter of the affected animal at a predetermined time after the transplantation. Examples of the affected animal include the same affected animal as mentioned above.

The method of the present embodiment can also be said to be a method for treating a kidney disease. As the organ for transplantation, those described above can be used.

By allowing the organ for transplantation which is transplanted in the step (a) to stand for a predetermined period, the organ for transplantation grows, and urine production is started. The predetermined period may refer to any period up to the organ for transplantation sufficiently grows, but before occurrence of hydronephrosis. The predetermined period may be appropriately adjusted depending on the symptoms and the like of the affected animal, but may be, for example, 1 to 10 weeks.

Subsequently, the step (b) is performed at a predetermined period of time (after 1 to 10 weeks) after transplantation. In the step (b), the bladder of the organ for transplantation and the ureter of the affected animal are connected. The ureter of the affected animal is connected to the bladder of the affected animal.

By connecting the bladder of the organ for transplantation and the bladder of the affected animal with the ureter of the affected animal, the urine produced by the organ for transplantation can be excreted to the bladder of the affected animal. More specifically, the urine produced by the kidney of the organ for transplantation is excreted to the bladder of the organ for transplantation through the ureter of the organ for transplantation, and then is excreted to the bladder of the affected animal from the bladder of the organ for transplantation through the ureter of the affected animal.

By the method of the present embodiment, the urine produced by the kidney of the organ for transplantation can be excreted to the bladder of the affected animal.

[Method for Treating Kidney Disease]

In one embodiment, the present invention provides a method for treating a kidney disease, including a step (a1) of transplanting a metanephros and a cloaca of a non-human animal into a body of an affected animal; a step (a2) of tissue-specifically removing a metanephric mesenchyme of a metanephros; a step (a3) of transplanting a kidney precursor cell to the metanephros, which is a step in which the transplanted kidney precursor cell is differentiated and matured to form a part of kidneys, and the cloaca is differentiated and matured to form a bladder so as to connect the bladder to the kidney via a ureter; and a step (b) of connecting the bladder to a ureter of the affected animal at a predetermined time after the transplantation of the kidney precursor cell. Examples of the affected animal include those mentioned above.

In the method of the present embodiment, the production (regeneration) of the kidney is performed in the body of the affected animal. The step (a2) and the step (a3) may be carried out in parallel. That is, a time of emptying the niche and a time of transplanting the kidney precursor cells may overlap. For example, the addition of the removing medicine and the transplantation of the kidney precursor cells may be carried out at the same time. Examples of the kidney precursor cells include the same kidney precursor cells as those for the above-described medical drug for kidney regeneration.

When a predetermined period has elapsed from the transplantation of the kidney precursor cells in the step (a3), the transplanted kidney precursor cells form the kidney, and urine production is started. The predetermined period may refer to any period up to the kidney and bladder sufficiently grow, but before occurrence of hydronephrosis. The predetermined period may be appropriately adjusted depending on the symptoms and the like of the affected animal, but may be, for example, 2 to 4 weeks.

Subsequently, the step (b) is performed at a predetermined period of time (after 2 to 4 weeks) after transplantation. In the step (b), the bladder formed by differentiation and maturation of the cloaca is connected to the ureter of the affected animal. The ureter of the affected animal is connected to the bladder of the affected animal.

The treatment method of the present embodiment may further include a step (a2′) in which the ureteric bud of the metanephros is tissue-specifically removed. As a result, not only the metanephric mesenchyme but also the ureteric bud can be replaced with cells derived from the transplanted kidney precursor cells derived from the non-human animal. As a result, it is possible to produce the kidney substantially consisting only of the cells derived from the transplanted kidney precursor cells derived from the non-human animal.

In a case of carrying out the step (a2′), any of the step (a2) and the step (a2′) may be carried out first, but after carrying out either one step thereof, it is preferable to provide a period of 4 to 7 days before carrying out the other step. Between the steps, transplanted kidney precursor cells derived from the non-human animal progress the development program to be differentiated.

The step (a2) and step (a3), or the step (a2′) and step (a3) may be carried out in parallel. That is, a time of emptying the niche and a time of transplanting the kidney precursor cells derived from the non-human animal may overlap. For example, the addition of the removing medicine and the transplantation of the kidney precursor cells derived from the non-human animal may be carried out at the same time.

For example, the step (a2) and step (a3) may be carried out at the same time first, and after a predetermined period, the step (a2′) and step (a3) may be carried out at the same time. Alternatively, the step (a2′) and step (a3) may be carried out at the same time first, and after a predetermined period, the step (a2) and step (a3) may be carried out at the same time.

EXAMPLES

Next, the present invention will be described in more detail by showing experimental examples, but the present invention is not limited to the following experimental examples.

Experimental Example 1

(Tissue-Specific Removal of Metanephric Mesenchyme in Mouse Embryo)

The iDTR mouse expressing the diphtheria toxin receptor (DTR) in the Cre recombinase activity-dependent manner was crossed with the Six2-Cre mouse in which the Cre recombinase gene was introduced into downstream of a promoter of Six2. Six2 is a transcription factor that is specifically expressed in the metanephric mesenchyme.

Subsequently, a mouse that expressed the diphtheria toxin receptor specifically in the metanephric mesenchyme was selected from an F₁ mouse on embryonic day 13, and the metanephros was extracted. The extracted metanephros was organ-cultured according to a standard method, and diphtheria toxin was added to the medium. As a result, Six2-positive kidney precursor cells of the metanephric mesenchyme, in which the diphtheria toxin receptor was expressed were killed. As a result, the metanephric mesenchyme was tissue-specifically removed.

Experimental Example 2

(Transplantation of Kidney Precursor Cells)

The kidney precursor cells derived from a wild-type mouse were prepared from the metanephros by a standard method and dissociated into single cells using a cell dissociation reagent. Subsequently, 1×10⁵ kidney precursor cells were transplanted into metanephros tissue from which the metanephric mesenchyme was tissue-specifically removed, which was prepared in Experimental Example 1. Thereafter, the organ culture of the metanephros tissue was continued.

Experimental Example 3

(Immunostaining 1 of Kidney Tissue)

The metanephros tissue of Experimental Example 2 was fixed with 4% paraformaldehyde after being cultured for 5 days from the transplantation of the kidney precursor cells, and therefore a tissue section sample was prepared. Subsequently, Six2 which is a marker of the metanephric mesenchyme and cytokeratin 8 which is a marker of the ureteric bud were immunostained, respectively. FIG. 3 is a fluorescence microscopy photograph showing the result of immunostaining. The magnification is 100 times. In FIG. 3, Six 2-positive cells are derived from the transplanted kidney precursor cells. In addition, cytokeratin 8-positive cells are derived from the host animal (F₁ mouse of Experimental Example 1).

As a result, it was confirmed that, using the ureteric bud derived from the F₁ mouse of Experimental Example 1 as a scaffold, the kidney precursor cells transplanted in Experimental Example 2 took over the development program of the host, autonomously advanced complicated differentiation induction, and thus formed the metanephric mesenchyme. This result shows that the cells constituting the metanephric mesenchyme can be replaced with the cells derived from the transplanted kidney precursor cells by the above-described method.

Experimental Example 4

(Immunostaining 2 of Kidney Tissue)

The kidney precursor cells derived from a transgenic mouse (GFP tg mouse) into which a green fluorescent protein (GFP) gene was introduced were prepared from the metanephros by a standard method and dissociated into single cells using a cell dissociation reagent. Subsequently, 1×10⁵ kidney precursor cells were transplanted into metanephros tissue from which the metanephric mesenchyme was tissue-specifically removed, which was prepared in the same manner as in Experimental Example 1. Thereafter, the organ culture of the metanephros tissue was continued.

Subsequently, the metanephros tissue was fixed with 4% paraformaldehyde after being cultured for 7 days from the transplantation of the kidney precursor cells, and therefore a tissue section sample was prepared. Subsequently, cytokeratin 8, which is a marker for the ureteric bud, and Wilms tumor suppressor protein-1 (WT1), which is a marker of glomerulus, were immunostained, respectively. Subsequently, fluorescence of GFP expressing the transplanted cells, and immunostained cytokeratin 8 and WT1 was observed with a fluorescence microscope. FIG. 4 is a fluorescence microscopy photograph showing the result of immunostaining. The magnification is 200 times. In FIG. 4, GFP-positive cells and WT1-positive cells are derived from the transplanted kidney precursor cells. In addition, cytokeratin 8-positive cells are derived from the host animal (F₁ mouse of Experimental Example 1).

As a result, it was confirmed that the transplanted kidney precursor cells derived from the GFP tg mice formed the glomeruli and kidney tubules. This result shows that it is possible to form functional kidney tissue from the kidney precursor cells by the method described above.

Experimental Example 5

(Regeneration of Kidney in Living Body of Mouse)

In the para-aortic region of the wild-type mouse, the cloaca and the metanephros tissue-specifically expressing the diphtheria toxin receptor in the metanephros tissue, which are obtained by crossing the iDTR mouse with Six2-Cre mouse, were transplanted.

Subsequently, by administering the diphtheria toxin, the metanephric mesenchyme of the metanephros was removed, and 1×10⁵ kidney precursor cells derived from the GFP tg mouse were transplanted. Subsequently, a mouse transplanted with the metanephros was raised for 7 days.

Subsequently, an abdominal cavity of the above-mentioned mouse was opened to observe the kidney (regenerated kidney) formed from the transplanted metanephros.

(a) of FIG. 5 is a photograph of a region where regenerated kidneys exist. The magnification is 15 times. The upper right shows the kidney of the wild-type mouse (host). The regenerated kidneys exist in a region surrounded by a dotted line near the center.

(b) of FIG. 5 is a photograph showing the observation result of the fluorescence of GFP in the same field of view as (a) of FIG. 5. The magnification is 15 times. As a result, fluorescence of GFP derived from transplanted kidney precursor cells was observed. This result indicates that the kidney regeneration was possible in the body of the mouse.

(a) of FIG. 6 is an optical micrograph of a tissue section sample prepared by fixing the above regenerated kidneys with 4% paraformaldehyde. The magnification is 400 times. In (a) of FIG. 6, the regenerated glomeruli were observed at a portion indicated by an arrowhead.

(b) of FIG. 6 is a fluorescence micrograph showing the observation result of the fluorescence of GFP in the same field of view as (a) of FIG. 6. The magnification is 400 times. In (b) of FIG. 6, fluorescence of GFP was observed at a portion indicated by an arrowhead. This result indicates that the regenerated glomeruli are derived from the transplanted kidney precursor cells.

Based on the above results, it became clear that the kidney regeneration can be performed in vivo.

Experimental Example 6

(Replacement of Both Metanephric Mesenchyme and Ureteric Bud of Mouse Embryo)

<<Tissue-Specific Removal of Ureteric Bud>>

In the present experimental example, the iDTR mouse having a genotype of Six2-Cre-ER^(tg/wt)HoxB7-Cre^(tg/wt) was used. First, in the same manner as in Experimental Example 1, the metanephros was extracted from the mouse embryo and subjected to organ-culture. Subsequently, diphtheria toxin was added to the medium to tissue-specifically remove the ureteric bud.

<<Transplantation of Kidney Precursor Cells>>

Subsequently, in the same manner as in Experimental Example 2, 1×10⁵ kidney precursor cells derived from the wild-type mouse were transplanted into the metanephros of the mouse, from which the ureteric bud was removed. Thereafter, the organ culture of the metanephros was continued for 5 days.

<<Tissue-Specific Removal of Metanephric Mesenchyme>>

Subsequently, tamoxifen and diphtheria toxin were added to the culture medium for organ culture. As a result, in the Six2-expressing cell, which is a metanephric mesenchyme-specific marker, Cre-ER is translocated into the nucleus and recombines to express the diphtheria toxin receptor. As a result, cells of the metanephric mesenchyme were killed by diphtheria toxin. As a result, the metanephric mesenchyme was tissue-specifically removed.

<<Transplantation of Kidney Precursor Cells>>

Subsequently, in the same manner as in Experimental Example 2, 1×10⁵ kidney precursor cells derived from the wild-type mouse were transplanted again into the metanephros of the mouse, from which the metanephric mesenchyme was removed. Thereafter, the organ culture of the metanephros was continued for 3 to 5 days.

<<Immunostaining>>

Subsequently, the metanephros after organ culture was fixed with 4% paraformaldehyde, and therefore a tissue section sample was prepared. Subsequently, the metanephros was immunostained with an anti-calbindin antibody for staining the ureteric bud and observed with a fluorescence microscope.

(a) of FIG. 7 is a representative photograph of the metanephros of a positive control. For the positive control, the diphtheria toxin was not added in the stage of removing the ureteric bud, and the kidney precursor cells were not transplanted. Therefore, in the positive control, tissues derived from the original ureteric bud were maintained.

(b) of FIG. 7 is a representative photograph of the metanephros of a negative control. For the negative control, the diphtheria toxin was added in the stage of removing the ureteric bud, and the kidney precursor cells were not transplanted. Accordingly, because in the negative control, the ureteric bud was tissue-specifically removed, and the kidney precursor cells were not transplanted, the ureteric bud was lost.

(c) of FIG. 7 is a representative photograph of the metanephros of a test group. In the test group, the ureteric bud was tissue-specifically removed, and the kidney precursor cells were transplanted. As a result, the ureteric bud was replaced by the transplanted kidney precursor cells, and the growth of tissues derived from the ureteric bud was observed.

Table 1 shows the results of measuring the number of ureteric bud tips in the metanephros of the positive control (n=5), the negative control (n=5), and the test group (n=5).

TABLE 1 Positive Negative Test control control group Number of ureteric bud tips 145.2 ± 22.2 73.2 ± 29.2 120.8 ± 23.8 (average value ± standard deviation)

As a result, in the negative control, a decrease in the number of ureteric bud tips was observed compared to the positive control. In contrast, in the test group, the same number of ureteric bud tips as the positive control was measured. This result shows that both metanephric mesenchyme and ureteric bud can be replaced with the transplanted kidney precursor cells by the method of the present experimental example.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide a technique for producing a kidney from kidney precursor cells. 

1. A kidney production method comprising: tissue-specifically removing kidney precursor cells in a metanephric mesenchyme of a metanephros of a first non-human animal; transplanting, into the metanephros, a kidney precursor cell derived from a second non-human animal which is allogeneic or xenogeneic to the first non-human animal; and advancing development of the metanephros, wherein the transplanted kidney precursor cell is differentiated and matured to form a part of the kidney.
 2. The kidney production method according to claim 1, further comprising: tissue-specifically removing an ureteric bud of the metanephros; and transplanting, into the metanephros, a kidney precursor cell derived from the second non-human animal which is allogeneic or xenogeneic to the first non-human animal.
 3. The kidney production method according to claim 1, wherein the kidney precursor cell is a cat cell.
 4. The kidney production method according to claim 1, wherein the non-human animal is a pig.
 5. The kidney production method according to claim 1, wherein the non-human animal is a mouse.
 6. The kidney production method according to claim 1, wherein the non-human animal is a cat.
 7. A kidney produced by the production method according to claim
 1. 8. A kidney comprising: a cell derived from a first non-human animal; and a cell derived from a second non-human animal which is allogeneic or xenogeneic to the first non-human animal, wherein a proportion of the cell derived from the second non-human animal which is allogeneic or xenogeneic to the first non-human animal is 70% by mass or more.
 9. The kidney according to claim 8, wherein the cell derived from the second non-human animal which is allogeneic or xenogeneic to the first non-human animal is a cat cell.
 10. A non-human animal comprising the kidney according to claim
 7. 11. An organ for transplantation, comprising: the kidney according to claim 7; a ureter; and a bladder.
 12. The organ for transplantation according to claim 11, wherein the ureter and the bladder are derived from the first non-human animal.
 13. A kit for kidney production, comprising: a metanephros of a first non-human animal; a medicine which tissue-specifically removes kidney precursor cells in a metanephric mesenchyme of the metanephros; and a kidney precursor cell derived from a second non-human animal which is allogeneic or xenogeneic to the first non-human animal.
 14. The kit for kidney production according to claim 13, further comprising a medicine which tissue-specifically removes an ureteric bud of the metanephros.
 15. A medical drug for kidney regeneration, comprising: a metanephros of a first non-human animal; a medicine which tissue-specifically removes kidney precursor cells in a metanephric mesenchyme of the metanephros; and a kidney precursor cell derived from a second non-human animal.
 16. The medical drug for kidney regeneration according to claim 15, further comprising a medicine which tissue-specifically removes an ureteric bud of the metanephros.
 17. A kidney transplantation method comprising: transplanting the organ for transplantation according to claim 11 into a body of an affected animal; and connecting a bladder of the organ for transplantation to a ureter of the affected animal at a predetermined time after the transplantation.
 18. A method for treating a kidney disease, comprising: (a1) transplanting a metanephros and a cloaca of a first non-human animal into a body of an affected animal; (a2) tissue-specifically removing kidney precursor cells in a metanephric mesenchyme of the metanephros; (a3) transplanting a kidney precursor cell into the metanephros, wherein the transplanted kidney precursor cell is differentiated and matured to form a part of a kidney, and the cloaca is differentiated and matured to form a bladder so as to connect the bladder to the kidney via a ureter; and (b) connecting the bladder to a ureter of the affected animal at a predetermined time after the transplantation of the kidney precursor cell. 